Search results for "Radio wave"
showing 10 items of 41 documents
Antennas for the detection of radio emission pulses from cosmic-ray induced air showers at the Pierre Auger Observatory.
2012
The Pierre Auger Observatory is exploring the potential of the radio detection technique to study extensive air showers induced by ultra-high energy cosmic rays. The Auger Engineering Radio Array (AERA) addresses both technological and scientific aspects of the radio technique. A first phase of AERA has been operating since September 2010 with detector stations observing radio signals at frequencies between 30 and 80 MHz. In this paper we present comparative studies to identify and optimize the antenna design for the final configuration of AERA consisting of 160 individual radio detector stations. The transient nature of the air shower signal requires a detailed description of the antenna s…
Measurement of the radiation energy in the radio signal of extensive air showers as a universal estimator of cosmic-ray energy
2016
We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8±0.7(stat)±6.7(syst) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principles calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the d…
A Non-Stationary Channel Model for the Development of Non-Wearable Radio Fall Detection Systems
2018
The emerging non-wearable fall detection systems rely on processing radio waves reflected off the body of the home user who has no active interaction with the system, increasing the user privacy and acceptability. This paper proposes a nonstationary channel model that is important for the development of such systems. A three-dimensional stochastic trajectory model is designed to capture targeted mobility patterns of the home user. The model is featured with a forward fall mechanism, which is actuated at a random point along the path. A transmitter emits radio waves throughout an indoor propagation environment, while a receiver collects fingerprints of the scattering objects on the emitted w…
The Impact of Human Walking on the Time-Frequency Distribution of In-Home Radio Channels
2018
Passive activity recognition of home occupants has become a very hot topic in the area of radio communications, as it enables the development of cutting-edge healthcare monitoring solutions. Thanks to ubiquitous radio waves, such as WiFi signals, at today's homes, one can process radio waves reflected off a person's body for identifying certain mobility patterns. This new approach ignores the need for any wearable sensors. This paper reports a challenging indoor radio channel measurement campaign at 5.9 GHz, which has been conducted to study the impact of walking persons on the temporal and spectral properties of the channel. In particular, the time-frequency distribution of the channel has…
The RFID technology for neurosciences: feasibility of limbs' monitoring in sleep diseases.
2009
This contribution investigates the feasibility of the passive UHF RF identification technology for the wireless monitoring of human body movements in some common sleep disorders by means of passive tags equipped with inertial switches. Electromagnetic and mechanical models as well as preliminary experimentations are introduced to analyze all the significant issues concerning the required power, the tag antenna design, the read distance, and the expected biosignals collected by the interrogation device.
How Do We Know If There’s a Message?
2010
As we have seen, radio waves can be excellent candidates for interplanetary communication, due to the fact that our galaxy is transparent to them. The problem lies in properly identifying the origin – artificial or natural – of an arriving signal. When we tune a radio receiver and we turn the antenna toward the cosmos, we gather hundreds of different signals. Even some of the natural signals are quite suggestive, and one can be tempted to consider them emissions from other civilizations.
Radio data and synchrotron emission in consistent cosmic ray models
2011
It is well established that phenomenological two-zone diffusion models of the galactic halo can very well reproduce cosmic-ray nuclear data and the observed antiproton flux. Here, we consider lepton propagation in such models and compute the expected galactic population of electrons, as well as the diffuse synchrotron emission that results from their interaction with galactic magnetic fields. We find models in agreement not only with cosmic ray data but also with radio surveys at essentially all frequencies. Requiring such a globally consistent description strongly disfavors very large ($L\gtrsim 15$ kpc) and, even stronger, small ($L\lesssim 1$ kpc) effective diffusive halo sizes. This has…
No effects of pulsed radio frequency electromagnetic fields on melatonin, cortisol, and selected markers of the immune system in man.
2001
There is growing public concern that radio frequency electromagnetic fields may have adverse biological effects. In the present study eight healthy male students were tested to see whether or not radio frequency electromagnetic fields as used in modern digital wireless telecommunication (GSM standard) have noticeable effects on salivary melatonin, cortisol, neopterin, and immunoglobulin A (sIgA) levels during and several hours after exposure. In a specifically designed, shielded experimental chamber, the circularly polarized electromagnetic field applied was transmitted by an antenna positioned 10 cm behind the head of upright sitting test persons. The carrier frequency of 900 MHz was pulse…
Feasibility study for a nanosatellite-based instrument for in-situ measurements of radio noise
2015
The radio environment on the earth is heavily affected by manmade sources such as radio transmissions, radars, and the like. The effect is particularly strong at MF frequencies and below, since the signals can propagate large distances via ionospheric bounce. Terrestrial magnetometer measurements have long been used to predict the Kp index, which is related to radio transmission at these ranges. Space weather measurements and models can also predict propagation of MF signals on the ground.
Influence of GSM signals on human peripheral lymphocytes: study of genotoxicity.
2013
Exposure to radiofrequency (RF) electromagnetic fields (EMF) is continuously increasing worldwide. Yet, conflicting results of a possible genotoxic effect of RF EMF continue to be discussed. In the present study, a possible genotoxic effect of RF EMF (GSM, 1,800 MHz) in human lymphocytes was investigated by a collaboration of six independent institutes (institutes a, b, c, d, e, h). Peripheral blood of 20 healthy, nonsmoking volunteers of two age groups (10 volunteers 16-20 years old and 10 volunteers 50-65 years old) was taken, stimulated and intermittently exposed to three specific absorption rates (SARs) of RF EMF (0.2 W/kg, 2 W/kg, 10 W/kg) and sham for 28 h (institute a). The exposures…